A Key to the Tropical African Hookeriales

F. Demaret & R. Potier de la Varde

Extracted from:
Demaret, F. & Potier de la Varde, R. 1951. Les espèces africaines du genre Cyclodictyon Mitt. Bull. Jard. Bot. Etat. Bruxelles 21:11-59.
Demaret, F. 1952. Complèment a l'etude des espèces africaines du genre Cyclodictyon Mitt. Bull. Jard. Bot. Etat. Bruxelles 22 :155-164
Demaret, F. & Potier de la Varde, R. 1952. Les espèces africaines du genre Callicostella (C.Muell.) Jaeg. Bull. Jard. Bot. Etat. Bruxelles 22:323-396.
Demaret, F. 1955. Étude preliminaire des Hookeriaceae africaines intertropicales Bull. Jard. Bot. Etat. Bruxelles 25(4):375-390.

Translated by C.R.Stevenson (Norfolk College, Tennyson Avenue, King's Lynn, Norfolk PE30 4DJ, UK.)

These translations are offered as a convenience only; plants can not be named safely without referring to the full original texts and illustrations, which clarify and amplify many points which are skipped over or neglected in the keys. The translations have attempted to follow the spirit of the original, rather than produce the exact word order. Some points may have been mistranslated or misunderstood - caveat emptor!

Since the 1950s a number of species have been added to the African flora; no attempt has been made to key them out. Where such additions have taken place, their presence has been noted at the start of each key to species. The Checklist of the mosses of sub-Saharan Africa (O'Shea, 1955) has been taken as the source for this data.

Key to genera
(click on the genus name to get the key to species)

1	Nerve absent or single	2
1	Nerve double	6

2	Nerve single	3
2	Nerve absent	Sauloma

3	Leaves dimorphic	4
3	Leaves all of same size and shape	Daltonia

4	Nerve single	5
4	Nerve bifurcating, into two unequal branches	Calyptrochaeta

5	Cells hexagonal - elongate; thin walled; peristome teeth not transversely striated; division line zig-zag	Distichophyllidium
5	Cells more-or-less isodiametric, often thick walled; peristome teeth transversely striate; line of division grooved	Distichophyllum

6	Leaves all of same size and shape	7
6	Leaves dimorphic	8

7	Cells papillose	Chaetomitrium
7	Cells smooth	Actinodontium

8	Leaves with only faint, or no border	9
8	Leaves distinctly bordered, cells lax, smooth, transparent	Cyclodictyon

9	Cells papillose	10
9	Cells smooth	11

10	Cells unipapillose	Callicostella
10	Cells 3-4 papillose	Glossadelphus

11	Lateral leaves not undulate when dry, falcate	12
11	Lateral leaves undulate when dry; not falcate	Hookeriopsis

12	Peristome teeth transversely striate, with a division line which is widely furrowed	Lepidopilidium
12	Peristome teeth papillose; dividing line zig-zagged	Lepidopilum

Attempts are being made to conserve the name Eriopus against Calyptrochaeta, but at present the latter is the correct name.

Key to Actinodontium

1	Forming bright green tufts; seldom nerved to beyond mid-leaf	*A. dusenii*
1	Forming dirty green tufts; leaf nerved to well beyond mid-leaf	*A. streptopogon*

Key to Callicostella

(Not keyed: C. ascensionis, C. papillata, C. papillata var. brevifolia, C. parvula, C. robillardei.)

NB. The leaves referred to are, unless otherwise stated, the lateral leaves.

1	Both nerves of some lateral and dorsal leaves, on well developed branches, more-or-less curved and converging towards the leaf apex, & nearly reaching the leaf margin	2
1	Nerves on lateral leaves straight, or only curved in their upper part, finishing well before the leaf apex. Lateral leaves rarely rounded at the apex	8

2	Lateral leaves, and often young leaves at the tip of branches, truncate, emarginate, or widely rounded at the apex	3
2	Lateral leaves, and especially the young ones at the ends of branches, widely obtuse, acute or acuminate, never emarginate. Old lateral leaves sometimes more-or-less truncate & sharply mucronate	7

3	Lateral leaves sometimes more-or-less emarginate at the apex, and not, or only feebly, papillose - or - clearly truncate / obtuse at apex and with prominent papillae. Width of upper cells at least 8µ wide. often more	4
3	Lateral leaves never emarginate at apex. Cell width in upper cells never more than 8µ	6

4	Leaves sometimes more-or-less emarginate at apex and not, or only feebly papillose. Nerves smooth / slightly crenulate at back	5
4	Leaves very rarely emarginate at apex, often truncate / obtuse, and with a central raised papilla	*C. erosotruncata*

5	Leaves sub-entire - serrulate, mainly emarginate at apex, with very small / indistinct / absent apical and central papillae. Nerves often curved right from the base, with one lying very close to the leaf edge	*C. emarginatula*
5	Leaves dentate / denticulate / eroded, the majority obtuse or truncate-mucronate, sometimes emarginate, with low more-or-less distinct central papillae. Nerves curving only in the upper part of the leaves	*C. subemarginatula*

6	Leaves largely rounded at apex. Central and parietal papillae very small	*C. parvocellulata*
6	Leaves generally obtuse / shortly obtuse, sometimes more-or-less pointed. Papillae (central, super-central, apical) elevated	*C. pusilla*

7	Nerves smooth, or crenulate / denticulate at back. Papillae low. No distinct pseudo-limbidium formed of one / several rows of elongated cells in the upper half of the leaves. Young leaves acute, never truncate at apex	*C. gabonensis*
7	Nerves more-or-less dentate at back. Papillae elevated. Pseudo-limbidium one / several cells wide sometimes present in lower half of leaves. Young leaves acute, never truncate at apex	*C. chevalieri*

8	Nerves smooth or hardly denticulate at back, not projecting or simply protuberant at the tip	9
8	At least one of the nerves more-or-less crenulate or dentate at back, and projecting, not dissolving in the tissue	14

9	Leaves 1-1.25mm long; more-or-less 18 cells wide between the two nerve endings	*C. tristis*
9	Leaves longer than 1.25mm. 25-30 cells between the tips of the two nerves	10

10	Upper cells clearly thickened at the angles	*C. tristis[C. applanata*]
10	Upper cells not, or only slightly thickened at the angles	11

11	Leaves oblongate / oval, never obtuse / rounded at apex. Upper cells 15-20(30)µ long and (6)10- 5µ wide	*C. leptocladula*
11	Leaves largely oval, often obtuse / rounded at apex	12

12	Upper leaf cells only slightly elongate; 8-12µ wide	13
12	Upper leaf cells elongate & 4-10µ wide	*C. perroti*

13	Upper leaf cells 10-18µ long	*C. laeviuscula*
13	Upper leaf cells (8)10-14(16)µ long	**C. laeviuscula var. latifolia**

14	Cells bearing very tiny papillae only on the angles of cell walls; plants sprouting on damp stones	*C. maclaudii*
14	Leaf cells with papillae other than those on the cell walls	15

15	Leaves with margins generally crenulate & denticulate, & only slightly eroded in their upper part	16
15	Leaves with margins clearly eroded / dentate, or simply dentate in their upper part	21

16	Plants with yellowish white more-or-less discoloured leaves. Lateral leaves 6 times as long as wide. Upper cells with a central conical papilla, larger than 4µ	*C. chionophylla*
16	Plants with green leaves; not discoloured. Lateral leaves a maximum of 3-4 times as long as wide. Upper cells with scarcely visible subapical papillae, or with a central subapical papilla and parietal papillae less than 4µ; generally easily visible	17

17	Upper cells often up to 20µ long with subapical papillae scarcely visible	*C. seychellensis*
17	Upper cells rarely as long as 20µ with low, but easily visible central / super-central / subapical papillae	18

18	Upper cells angular, with thin walls; (10)15-20µ long	*C. fissidentella*
18	Upper cells thickened, with more-or-less rounded angles; sometimes a little porose	19

19	Upper cells 6-14µ wide, with low papillae	*C. papillosulla*
19	Upper cells 6-10µ wide and with low, or more-or-less elevated papillae	20

20	Upper leaf cells 10-14(16)µ long; margin crenulate / denticulate / dentate, often bearing several papillae	*C. brevipes*
20	Upper leaf cells (10)12-20µ long; margin finely crenulate / denticulate, and with a single papilla per cell	*C. salaziae*

21	Upper leaf cells often up to 20µ long, and with low papillae	*C. seychellensis*
21	Upper leaf cells rarely as long as 20µ	22

22	Upper leaf cells not, or only slightly thickenedat the angles, and non-porose. Back of nerves on most leaves, crenulate / denticulate at tip	23
22	Upper leaf cells clearly thickened at the angles, and with more-or-less porose walls. Tip of nerves dentate at back	24

23	Upper leaf cells 8-12(14)µ long, 6-8µ wide. Lateral leaves strongly widened in their lower part	*C. attenuata*
23	Upper leaf cells 14-16(20)µ long x (6)8-10µ wide. Leaves not widened below	*C. lacerans*

24	Majority of upper cells 15µ or more long. Walls thickened, and more-or-less porose	*C. perpapillata*
24	Majority of upper cells 15µ long or less. Walls thin, or only slightly thickened, and not, or only slightly, porose	25

25	Central / super-central papillae present on the majority of the upper leaf cells	26
25	Papillae on the majority of upper leaf cells apical / sub-apical	27

26	Upper leaf cells bearing large papillae. Nerves often winged / toothed at back, with teeth divided into two by strongly projecting ventral & dorsal papillae	*C. usambarica*
26	Upper leaf cells with fairly small papillae. Nerves simply toothed at back	*C. brevipes*

27	Upper leaf cells rarely more than 12µ long. Parietal papillae absent or rare	*C. africanum*
27	Upper leaf cells often more than 12µ long. Parietal papillae frequent.	*C. constricta*

Key to Chaetomitrium

1	Leaves narrowly spreading (upright); nerve short but distinct	2
1	Leaves spreading / squarrose; nerve absent or indistinct	*C. borbonicum*

2	Leaves serrulate	*C. dusenii*
2	Leaves sub-entire	*C. comorense*

Key to Cyclodictyon

(Not keyed: C. albicans, C. annobonense and C. vesiculosum. Only the latter, so far, has been found on the African mainland.)

NB. Throughout this key the leaves referred to are the lateral leaves.

1	Borders of lateral leaves 2-3 (4) cells wide at leaf apex, and very distinct	2
1	Borders of lateral leaves 1-2 cells wide at apex, more or less distinct	8

2	Lateral leaves 10-25 cells wide in their upper part (ie about 2/3rds of the way up the leaf, just before it begins to narrow. Counts should be made on several well developed stem leaves)	21
2	Lateral leaves 30-45 cells wide in their upper part	3
2	Lateral leaves 45-55 cells wide in their upper part; entire or subentire at apex	7

3	Lateral leaves oval; majority of cells at leaf apex clearly elongate, 2-3 (4) times longer than wide	4
3	Lateral leaves widely oval; majority of cells at leaf apex almost isodiametric, or at most 2 times as long as wide	5

4	Lateral leaves dentate denticulate at apex; cells 35-60µ x 15-25µ	*C. borbonicum*
4	Lateral leaves subentire at apex. Cells 30-40µ x 12-18µ	*C. perlimbatum*

5	Leaves at least, and generally longer than, 2.75mm. Border 3-4 cells wide in mid-leaf	*C. laete-virens*
5	Leaves generally leass than 2.75mm long. Borders 2-3 cells wide about mid-leaf	6

6	Leaves dentate; 2.25-2.75mm long, and about 1mm wide. Cells at leaf apex 30-40µ long, x 20-30µ wide	*C. brevifolium*
6	Leaves entire / sub-entire; 2 - 2.25µ x 15-20µ	*C. subbrevifolium*

7	Leaves 3mm + long; nerves about 50µ wide at base. Borders hyaline; 3 cells wide at mid-leaf. Cells at leaf apex 30-50µ long	*C. crassicaule*
7	Leaves < 3mm long; nerves 40µ wide at base. Borders opaque; 2 cells wide at mid-leaf. Cells at apex 25-30µ long	*C. preussii*

8	Leaves about 30 cells wide in the upper 2/3rds of the leaf, before it begins to narrow	9
8	Leaves between 10-25 cells wide in the upper 2/3rds, before starting to narrow	13

9	Aquatic plants. Cells at leaf apex 14-20µ wide	*C. immersum*
9	Terrestrial plants. Cells at leaf apex 20-40µ wide	10

10	Leaves with a terminal apiculus 60-100µ long	11
10	Leaves with a broad terminal mucron 25µ long	*C. subobtusifolium*

11	Leaves sub-obtuse, apiculate; slightly denticulate at the tip. Cells at leaf apex 30-(40)µ wide	*C. krebedjense*
11	Leaves widely acute, deeply denticulate at tip. Cells at apex 25µ wide	**C. krebedjense var. argutidens**

12	Nerves smooth at back, not terminating in a spinose or blunt toot	*C. filicuspes*
12	Nerves denticulate at back, ending in a spinose or blunt tooth	13

13	Leaves acute / very acuminate. Acumen generally >150µ long	14
13	Leaves generally obtuse or sub-obtuse, rarely widely acute & briefly acuminate (acumen generally < 100µ long)	15

14	Leaves 2.5 - 3mm long, dentate at apex; circa 18 - 25 cells wide before leaf begins to narrow. Nerves 30 - 40µ wide at base	*C. vallis-gratiae*
14	Leaves 1.5 - 2mm long, feebly denticulate at apex. About 15 cells wide before leaf begins to narrow. Nerves 20 - 25µ wide at base	*C. auberti*

15	Leaves 2 - 3mm long; generally > 1mm wide	16
15	Leaves c. 2mm long; generally < 1mm wide	19

16	Nerves < 25µ wide at base. Leaves very asymmetric; about 17 cells wide at nerve endings. At greatest leaf width, distance from nerve to leaf edges respectively 5 & 12 cells wide	*C. hildebrandti*
16	Nerves > 25µ wide at base (30 - 70µ); leaves only slightly asymmetric; 20 - 25 cells wide at nerve endings. At max. leaf width 12-14 and 18-20 cells lie between the nerves and the leaf margins	17

17	Cells generally as wide at midleaf as at leaf tip; 40 - 45µ wide	*C. recognitum*
17	Cells at mid-leaf generally narrower than at leaf tip	18

18	Cells at leaf apex 25 - 35µ wide. Leaves obtuse or sub-obtuse, and shortly apiculate or mucronate (apiculus 60µ long)	*C. lebrunii*
18	Cells at leaf apex 32 - 55µ wide. Leaves sub-obtuse or widely acute, ending in an apiculus 100µ wide	*C. spectabile*

19	Majority of marginal cells at leaf apex < 40µ long	*C. perrotetii*
19	Majority of marginal cells at leaf apex > 40µ long	20

20	Leaves crenulate, sub-denticulate at apex. Cells at leaf apex uniformly wide (40 - 50µ). Cell walls 1 - 2µ wide	*C. delicatulum*
20	Leaves dentate at apex. Cells at apex non uniform in thickness (20 - 45µ); cell walls often sub-thickened by chlorophyll: up to 4µ wide	**C. vallis-gratiae forma breutelianum** [taxon not recognised in O'Shea]

21	Nerve smooth at back; not finishing in a spiny or blunt tooth	C. filiscupes
21	Back of nerve denticulate and ending in a spiny or blunt tooth	22

22	Lateral leaves longly acuminate, not shortly tapered. 12-15 cells wide towards the nerve tip of lateral leaves	23
22	Lateral leaves more-or-less shortly acuminate, often shortly tapered at the tip. 15-25 cells wide towards the nerve tip of lateral leaves	24

23	Lateral leaves dentate / denticulate at the margin in the upper 1/4. Upper cells of lateral leaves 50-100 µm long. Leaf margins uniseriate	*C. dixonianum*
23	Lateral leaves only feebly denticulate in upper 1/4. Cells 40-60 µm long. Leaf margins biseriate	*C. aubertii*

24	Terminal apiculus of lateral leaves generally bidentate at tip. Nerves clearly dentate dorsally. Upper leaf cells of lateral leaves 50-80 µm long	*C. bidentatum*
24	Terminal apiculus of lateral leaves ending in a simple point. Back of nerves generally bluntly toothed. Upper cells 25-60 µm long	*C. vallis-gratiae*

Key to Daltonia

(Not keyed: D. angustifolia, D. constricta, D. forsythii, D. longinervis, D. onraedtii, D. splachnoides.)

1	Leaves with margin plane , or revolute on one side only	2
1	Leaves with revolute borders	7

2	Leaves finely denticulate	3
2	Leaves entire	5

3	Nerve reaching to leaf tip	*D. dusenii*
3	Nerve vanishing in mid-leaf	4

4	Pedicel straight; capsules sub-globose	*D. latimarginata*
4	Pedicel curved at top; capsule oblong	**D. latimarginata var. madagassa**

5	Leaves less than 1.3mm long	*D. minuta*
5	Leaves 1.5mm or more	6

6	Leaves broadly lanceolate, spreading, with plane margins	*D. mittenii*
6	Leaves narrowly lanceolate, slightly recurved, margin plane, or revolute on one margin only	*D. cardotii* [D. intermedia]

7	Leaf nerved to near tip	*D. longinerva*
7	Leaf nerved to mid-leaf, or ending below tip	8

8	Differentiated margin / border greater than half leaf width	*D. euryloma*
8	Border less than half width of leaves	9

9	Border 3-4 cells wide at base	10
9	Border 7-12 cells wide at base	11

10	Pedicel scabrous / papillose; cells 20-30µ long	**D. angustifolia var. strictifolia**
10	Pedicel smooth; cells 35-40µ long	*D. tortifolia*

11	Border 7-8 cells wide at base; pedicel papillose or smooth at summit	12
11	Border 10-12 cells wide at base; pedicel smooth	*D. plicata*

12	Pedicel scabrous at summit	*D. mildbraedii*
12	Pedicel smooth	**D. mildbraedii var. laevis**

Key to Distichophyllidium

Only one African species: D. africanum.

Key to Distichophyllum

(Not keyed: D. annobonense, D. mniifolium, D. rakatomorie.)

1	Leaves more-or-less undulate	2
1	Leaves flat	*D. procumbens*

2	Stems 1.75cm high; border 3-4 cells wide; calyptra scabrous	*D. mascarenicum*
2	Stems 4-5 cm high; border two cells wide; calyptra smooth	3

3	Leaves highly crisped, 3.5 + mm long	*D. rigidicaule*
3	Leaves undulate, less than 3 mm long	**D. rigidicaule var. gabonense**

Key to Calyptrochaeta (=Eriopus)

Only one African species: C. asplenioides

(Calyptrochaete cristata only occurs in Mauritius, from which C. asplenioides is not yet known.)

Key to Glossadelphus

(These are treated as synonyms in the sub-Saharan Africa moss checklist.)

1	Nerve small / indistinct	*G. guineensis*
1	Nerves distinct	2

2	Leaf nerved to 1/4 length	*G. abruptus*
2	Leaf nerved to 1/2 way	3

3	Leaves spreading, flat, sub-homomallous, rounded at tip. Pedicel fairly smooth, 5-7 mm long	*G. viridis*
3	Leaves spreading, not homomallous, often truncate, sometimes emarginate. Pedicel scabrous to summit, 10-12 mm long	*G. semiscabrus*

Key to Hookeriopsis

(Not keyed: H. pocsii, H. angolense, H. balazsii, H. darntyi, H. pallidifolia.)

1	Denticulation simple; not obviously double	2
1	Marginal denticulation double	7

2	Upper end of cells papillose	*H. papillosula*
2	Cells non-papillose	3

3	Leaves denticulate; cells rounded-hexagonal	4
3	Leaves markedly toothed, teeth occasionally twinned; cells elongate-hexagonal	5

4	Leaves narrowly knife-shaped; width not more than 1/4 length	*H. staudtii*
4	Leaves broadly knife-shaped. Width roughly half length	*H. cheiloneuron*

5	Leaves broadly acute	*H. ambigua*
5	Leaves acuminate, especially the lower ones	6

6	Leaves very concave; nerve double	*H. pappeana*
6	Leaves flat; nerve sometimes single, sometimes double	*H. diversifolia*

7	Leaves longly and gradually acuminate; strongly toothed	*H. gabonensis*
7	Leaves abruptly acuminate; weakly toothed	*H. mittenii*

Key to Lepidopilidium

(Not keyed: L. brunneolum, L. flexuosum, L. parvulum. L. cyrtostegium appears in O'Shea under Lepidopilum.)

1	Pedicel 7 mm or less long	2
1	Pedicel 10 mm + long	9

2	Pedicel smooth or nearly so	3
2	Upper part of pedicel papillose or rough	5

3	Leaf nerved to 1/3 length	*L. theriotti*
3	Leaf nerved to half length	4

4	Pedicel almost smooth for 2-5 mm. Spores 10-15µ	*L. hanningtonii*
4	Pedicel smooth for 5-7 mm. Spores 6-7µ	*L. chenagonii*

5	Leaf nerved to 1/3 length. Capsule upright	6
5	Leaf nerved to mid-leaf. Capsule horizontal	7

6	Median leaf cells 125µ or less wide. Spores 10-15µ	*L. subdevexum*
6	Mid-leaf cells to 150µ. Spores 10µ	**L. subdevexum var. intermedium**

7	Leaves longly acuminate with revolute margins. Annulus present	*L. attenuatum*
7	Leaves shortly acuminate. Annulus absent	8

8	Leaf margin plane. Spores 25µ diameter	*L. corbieri*
8	Leaf margins slightly revolute. Spores 10-15µ diameter	*L. devexum*

9	Pedicel roughened at summit. Leaf margin revolute	*L. subrevolutum*
9	Pedicel smooth or only very slightly roughened at the top. Leaf margins plane	10

10	Leaf nerved to mid-leaf & beyond. Perichaetial leaves dentate	*L. caespitosum*
10	Leaf nerved to less than half way. Perichaetial leaves entire	*L. isleanum*

Key to Lepidopilum

(Not keyed: L. verrucipes. L. cyrtostegium appears in O'Shea under Lepidopilidium.)

1	Plants silvery	*L. niveum*
1	Plants not silvery	2

2	Stems normally > 2 cm	3
2	Stems normally < 2 cm	5

3	Leaves denticulate. Stems 5 mm long	*L. carrougeauanum*
3	Leaves obviously toothed. Stems 10-20 mm long	4

4	Capsule horizontal; pedicel roughened	*L cyrtostegium*
4	Capsule erect; pedicel warty	*L. verrucipes*

5	Lateral leaves nerveless, or only weakly nerved	*L callochlorum*
5	Lateral leaves with well developed nerves normally reaching to mid-leaf	6

6	Leaf axils filamentous. Calyptra smooth	7
6	Leaf axils without filaments. Calyptra scaly	9

7	Stem 4-5 cm long. Pedicel 3-4 mm	8
7	Stem 7 cm long. Pedicel 7 mm	*L. filiferum*

8	Pedicel prickly. Propagules present	*L. hirsutum*
8	Pedicel tuberculate. Propagules absent	**L. hirsutum var. tuberculatum**

9	Stem 2.5 cm long. Pedicel 3-4 mm	*L. lastii*
9	Stem 5 cm long. Pedicel 10 mm	*L. dusenii*

Key to Sauloma

(Not keyed: S. africana. S. humblotii appears in O'Shea under Lepidopilium.)

1	Basal cells scarcely differentiated. Mid-leaf cells 90-100µ x 20-25µ	*S. humblotii*
1	Basal cells differentiated in at least 4 ranks. Mid-leaf cells 35-40µ x 10µ	*S. tisserantii*

Reference

O'Shea, B. 1995. Checklist of the mosses of sub-Saharan Africa. Tropical Bryology 10:91-198.

TBG35/hookey Issue 2 - 04.04.97